There's no such thing as free mods, well that give you any real power increase anyway. Just optimize what you have, good tune up, proper valve adjustment, clean filters, good oil, make sure your brakes aren't dragging, dump any extra weight you don't really need. If your looking for more power it's there, it's just gonna cost you. I suppose you could advance your timing a couple of degrees and run premium, but that's still not " free." Premium costs more. There is a lot of info on this forum about making these engines more powerful, but I've never seen any real gains for " free."